Legend for Class
Diagram

In a class diagram,
we visually distinguish the different kinds of Java entities, as
follows:

The interface: A
rounded rectangle

The class: A
rectangle

The abstract
class: A rectangle with an empty dot

The final
class: A rectangle with a black dot

Classes with
subclasses: A rectangle with a small black triangle on the
lower right corner

Most of these elements
are shown below. The class or interface being described in the
current chapter is shaded grey (this is not applicable for package
class diagrams). A solid line represents extends , while a
dotted line represents implements .